Exploiting the valley degree of freedom introduces a novel paradigm for advancing quantum information technology. Currently, the investigation on spontaneous valley polarization mainly focuses on two major types of systems. One type magnetic systems by breaking the time-reversal symmetry, the other is ferroelectric materials through breaking the inversion symmetry. Might there be additional scenarios? Here, we propose to realize spontaneous valley polarization by breaking the mirror symmetry in the altermagnets, named type III valley polarization. Through symmetry analysis and first-principles calculations, we confirm that this mechanism is feasible in Non-Janus Fe2WS2Se2. Monolayer Non-Janus and Janus Fe2WS2Se2 are stable Neel-type antiferromagnetic state with the direct band gap semiconductor. More interestingly, their magnetic anisotropy energy exhibits the rare biaxial anisotropy and a four-leaf clover shape in the xy plane, while the xz and yz planes show the common uniaxial anisotropy. This originated from the fourth-order single ion interactions. More importantly, the valley splitting is spontaneously generated in the Non-Janus Fe2WS2Se2 due to the Mxy symmetry breaking, without requiring the SOC effect. Both the Non-Janus and Janus Fe2WS2Se2 exhibit diverse valley polarization and anomalous valley Hall effect properties. In addition, the magnitude and direction of valley polarization can be effectively tuned by the biaxial strain and magnetic field. Our findings not only expand the realization system of spontaneous valley polarization, but also provide a theoretical basis for the high-density storage of valley degrees of freedom.

Magnons,as quasiparticles arising from spin wave excitations in magnetic materials,have demonstrated significant application potential in quantum information technology,spintronics,and microwave engineering in recent years.The cavity magnon optomechanical system,serving as a key platform for investigating magneto-optical interactions,has advanced the exploration of nonlinear dynamical behaviors and the innovative design of quantum devices through strong coupling between magnons,photons,and phonons.However,traditional single-cavity systems face limitations in terms of tunability,long-range interactions,and nonlinear enhancement,making them insufficient for complex quantum control requirements.In recent years,dual-cavity systems have become a research hotspot due to their multidimensional control capabilities achieved through inter-cavity coupling,such as photon mode splitting and enhanced nonlinear Kerr effects.Meanwhile,semiconductor quantum dots,provide a novel pathway for regulating magnon dynamics due to their tunable nonlinear response characteristics.In this work,we construct a novel coupled quantum system by integrating quantum dots and a dual-cavity architecture,and investigate the bistable phenomena under both forward and backward driving field inputs.By comparing the third-order nonlinear equations governing magnon populations in the two scenarios,we derive the impedance matching condition.When this condition is satisfied,the magnon responses induced by forward driving field and backward driving field are identical.Conversely,under impedance mismatch,the magnon responses exhibit different behaviors.Specifically,when the impedance matching condition is violated,the dual-cavity magnon optomechanical system incorporating three-level quantum dot molecules exhibits a lower bistability threshold than its counterpart without quantum dots.This allows for a transition from low steady state to high steady state while reducing the driving field strength,thereby achieving switching functionality at lower input power.Furthermore,we establish a multiparameter cooperative control model,revealing a three-dimensional parameter space formed by tunneling coupling,cavity-quantum dot coupling,and inter-cavity coupling.By adjusting these coupling strengths,the bistability threshold and hysteresis loop width can be effectively controlled,thereby modulating the driving field intensity required for bistability.This system is expected to experimentally observe the magnonic bistability through the vector network analyzer-based detection of abrupt changes in transmission or absorption windows in reflection spectra.Such capabilities can advance data signal transmission,switching devices,and memory technologies,and has the potential to serve as components of large-scale quantum information processing units.Additionally,this research may find important applications in the field of magnetic spintronics.

Compared to the ferromagnetic materials that realize the anomalous valley Hall effect by breaking time-reversal symmetry and spin-orbit coupling, the antiferromagnetic materials with the joint spatial inversion and time-reversal (PT) symmetry are rarely reported that achieve the anomalous valley Hall effect. Here, we predict that the antiferromagnetic monolayer MnBr possesses spontaneous valley polarization. The valley splitting of valence band maximum is 21.55 meV at K and K' points, which is originated from Mn-dx2-y2 orbital by analyzing the effective Hamiltonian. Importantly, monolayer MnBr has zero Berry curvature in the entire momentum space but non-zero spin-layer locked Berry curvature, which offers the condition for the anomalous valley Hall effect. In addition, the magnitude of valley splitting can be signally tuned by the onsite correlation, strain, magnetization rotation, electric field, and built-in electric field. The electric field and built-in electric field induce spin splitting due to breaking the P symmetry. Therefore, the spin-layer locked anomalous valley Hall effect can be observed in MnBr. More remarkably, the ferroelectric substrate Sc2CO2 can tune monolayer MnBr to realize the transition from metal to valley polarization semiconductor. Our findings not only extend the implementation of the anomalous valley Hall effect, but also provides a platform for designing low-power and non-volatile valleytronics devices.

This paper investigates optical bistability in a dual-cavity optomechanical system for optical switching applications. The hybrid configuration integrates an optical cavity with Kerr media and a mechanical resonator embedding semiconductor double quantum dot molecules. By solving steady-state Heisenberg-Langevin equations, we derive photon number expressions revealing bistable behavior. Numerical simulations demonstrate that bistability thresholds and hysteresis width can be tuned via external parameters (magnetic field intensity, probe frequency) and internal parameters (inter-cavity coupling strength, Kerr coefficient, quantum dot tunneling). The system's absorption response to the probe field shows dual-control mechanisms: external fields modulate medium interactions, while internal parameters adjust energy exchange dynamics. A novel optical switch design is proposed based on this controllable bistability. These findings highlight the system's potential for developing sensitive optical switches, optical memory devices, and photonic logic circuits.

The best carrier for quantum information transmission is light signal, which has a fast propagation speed and can carry a large amount of information. However, during the propagation of light, dispersion effect and diffraction effect can cause quantum information to be distorted to a certain extent. On the contrary, optical solitons are formed due to the balance between the system’s dispersion (diffraction) effect and nonlinear effect, and they exhibit very high stability and fidelity. Therefore, they have received widespread attention in electromagnetically induced transparency (EIT) media with ultracold atoms. However, cold atomic gas media require extremely low operating temperatures, and the performances of the materials are difficult to control precisely. These factors are unfavorable for the miniaturization and integration of future information devices, thus significantly limiting their practical applications. Semiconductor quantum dot media, on the other hand, possess advantages such as discrete energy level structures and spectral properties similar to those of cold atomic gases, longer decoherence times, larger electric dipole moments, more significant nonlinear optical effects, and easy integration, making them an ideal alternative to cold atomic media. In this work, semiconductor quantum dots are coupled with optical fibers, the most common carrier in optical communication, to explore the formation, storage, and retrieval of temporal optical solitons in the coupled system. The results show that due to the tunneling-induced transparency effect between dots in semiconductor quantum dot molecules, light absorption in the system is greatly suppressed. At the same time, the transverse confinement of the nanofiber can enhance the interaction between light and the system, and the enhanced nonlinear response of the system can balance the dispersion effect, resulting in stable temporal optical solitons. Further research indicates that by turning on and off the inter-dot tunneling coupling, the high-efficiency and high-fidelity storage and retrieval of optical solitons can be realized in the system. These findings have certain guiding significance and potential application value for the processing all-optical information in solid quantum materials.

Bohm potential and electron spin are very important quantum effects in quantum plasma. In certain circumstances, they may have important influences on the interaction of electromagnetic wave and plasma. In this paper, we make a comparison of spin force and Bohm potential force in Gaussian laser pulse-magnetized quantum plasma, and clarify which force plays the main role under different conditions. It is shown that for long Gaussian pulse, which force will prevail depends on the ratio of lambda(2)(p)/ L-p(2) and the normalized potential a. And for short Gaussian pulse, if a < 0.2, the Bohm potential force is greater than the spin force, and if a > 0.2, the spin force will dominate the Bohm potential force.

The color of the diamond obtained with the B2S3 additive changes from yellow to light blue and the resistivity of the synthesized diamond drops from 3.89 × 10 Ω cm to 2.51 × 10−1 Ω cm with the introduction of Ti/Cu into the synthetic cavity.

The spin effects on the propagation characteristic of circularly polarized electromagnetic (EM) wave in high density strongly magnetized plasma are discussed based on the the classical hydrodynamical model of relativistic spin plasma. The dielectric coefficients for right-hand circularly polarized (RCP) and left-hand circularly polarized (LCP) waves are obtained. Results show that the spin effects can affect the propagation characteristic of circularly polarized EM wave dramatically. Provided the spin effect is strong enough, LCP waves can also propagate in the magnetized over-dense plasma, while RCP waves may not. The strength of spin effects can be enhanced by increasing the plasma density or/and EM wave intensity.

Hourglass loop in two-dimensional (2D) systems is typically vulnerable against spin–orbit coupling (SOC). Here, we explore 2D systems with a type of spin-polarized nodal loop that is robust under SOC and characteristic of an hourglass-type dispersion. Through first-principles calculations, we identify the monolayer VCl2 materials as a realistic material platform to realize an hourglass loop. There exist three phases, all of which are dynamically stable. For the γ-structure, as a new single spin hourglass loop material. It shows semiconducting and gapless properties in spin down and spin up channels, respectively. Moreover, it always exhibits an hourglass loop property in the absence and presence of SOC. It indicates that the hourglass has strong against SOC. Our work suggests a realistic material platform for investigating the novel physics associated with band crossings in 2D systems.

In this study, we analyzed the storage and retrieval of vector optical fields in semiconductor double quantum dots with interdot tunneling coupling. Our findings indicate that temporal vector optical solitons (TVOS) can be effectively stored and retrieved through this coupling. Furthermore, we conducted numerical simulations to investigate the interaction between TVOS. Our results suggest that the interaction between in-phase solitons is attractive, while the interaction between anti-phase solitons is repulsive. Additionally, we found that TVOS remain stable even after a collision, which is significant for the processing of optical information in solid quantum materials. Overall, our study sheds light on the potential of interdot tunneling coupling for storing and retrieving vector optical fields in semiconductor double quantum dots. Additionally, our findings regarding the interaction between TVOS can inform future research in the field of optical information processing.

Under the condition of 5.6 GPa and 1250–1450 ℃, the diamond single crystals are synthesized in a cubic anvil high-pressure and high-temperature apparatus. High-purity FeNiCo solvents or NiMnCo solvents are chosen as the catalysts. High-purity (99.99%) graphite powders selected as a carbon source. High-quality abrasive grade diamond single crystals with relatively developed (100) or (111) crystal planes are used as crystal seeds. The effects of catalyst composition on crack defects in diamond single crystals are studied carefully. Firstly, using FeNiCo and NiMnCo catalysts respectively, we carry out the diamond single crystal growth experiments. It is found that under the same crystal growth condition, the probability of crystal crack defects in diamond single crystals grown with FeNiCo catalyst is significantly higher than that of crystals grown with NiMnCo catalyst. We believe that this is related to the high viscosity, poor fluidity of FeNiCo catalyst melt, and the large specific surface area of the crystal during growth, which leads to its high requirements for the stability of growth conditions. Secondly, the relationship between the growth time and the limit weight gain speed of the diamond single crystal synthesized, respectively, by FeNiCo catalyst and NiMnCo catalyst are investigated. The results are shown below. 1) The limiting growth rate of diamond single crystal increases with the growth time going by. 2) In the same growth time, the limit growth rate of diamond crystal grown with NiMnCo catalyst is higher than that of diamond crystal grown with NiMnCo catalyst. Thirdly, by scanning electron microscopy (SEM), we calibrate the surface morphology of the synthesized diamond single crystal. The test results show that the diamond single crystal has a high surface flatness. Even for the crystals with crack defects in the interior, the surface flatness is still good. However, Fourier transform infrared (FTIR) measurements show that the nitrogen impurity content of diamond crystal grown by FeNiCo catalyst with crack defect is about 3.66×10–4. The content of nitrogen impurity in the crystal grown by NiMnCo catalyst without crack defect is about 4.88×10–4. The results show that there is no direct correlation between nitrogen impurity content and crack defects in diamond crystal.

In the paper, under 5.6 GPa and 1250-1450℃, the diamond single crystals were synthesized in a cubic anvil high pressure and high temperature apparatus. High-purity FeNiCo solvents or NiMnCo solvents were chosen as the catalysts. High-purity graphite powder (99.99%, purity) was selected as the carbon source. High quality abrasive grade diamond single crystals with relatively developed (100) or (111) crystal planes were used as crystal seeds The effects of catalyst composition on crack defects in diamond single crystals were studied carefully. At first, using FeNiCo and NiMnCo catalysts respectively, we carried out diamond single crystal growth experiments. It is found that under the same crystal growth conditions, the probability of crystal crack defects in diamond single crystals grown with FeNiCo catalyst is significantly higher than that of crystals grown with NiMnCo catalyst. We believe that this is related to the high viscosity, poor fluidity of FeNiCo catalyst melt and the large specific surface area of the crystal during growth, which leads to its high requirements for the stability of growth conditions. Secondly, the relationship between the growth times and the limit weight gain speed of the diamond single crystals synthesized by choosing FeNiCo catalyst and NiMnCo catalyst were investigated. The results show that: (i) The limiting growth rate of diamond single crystals increases with the growth time. (ii) At the same growth time, the limit growth rate of diamond crystal grown with NiMnCo catalyst is higher than that of diamond crystal grown with NiMnCo catalyst. Thirdly, by means of scanning electron microscopy (SEM), we calibrated the surface morphology of the synthesized diamond single crystals. The test results show that the diamond single crystal has a high surface flatness. Even for crystals with crack defects in the interior, the surface flatness is still good.. However, by Fourier transform infrared (FTIR) measurements, the researchers obtained that the nitrogen impurity content of diamond crystal grown by FeNiCo catalyst with crack defect is about 366 ppm. The content of nitrogen impurity in the crystal grown by NiMnCo catalyst without crack defect is about 488 ppm. The results show that there is no direct correlation between nitrogen impurity content and crack defects in diamond crystals.

Crystallization of diamond with different nitrogen concentrations was carried out with a FeNiCo–C system at pressure of 6.5 GPa. As the nitrogen concentration in diamond increased, the color of the synthesized diamond crystals changed from colorless to yellow and finally to atrovirens (a dark green). All the Raman peaks for the obtained crystals were located at about 1330 cm −1 and contained only the sp 3 hybrid diamond phase. Based on Fourier transform infrared results, the nitrogen concentration of the colorless diamond was < 1 ppm and absorption peaks corresponding to nitrogen impurities were not detected. However, the C-center nitrogen concentration of the atrovirens diamond reached 1030 ppm and the value of A-center nitrogen was approximately 180 ppm with a characteristic absorption peak at 1282 cm −1 . Furthermore, neither the NV 0 nor the NV − optical color center existed in diamond crystal with nitrogen impurities of less than 1 ppm by photoluminescence measurement. However, Ni-related centers located at 695 nm and 793.6 nm were observed in colorless diamond. The NE8 color center at 793.6 nm has more potential for application than the common NV centers. NV 0 and NV − optical color centers coexist in diamond without any additives in the synthesis system. Importantly, only the NV − color center was noticed in diamond with a higher nitrogen concentration, which maximized optimization of the NV − /NV 0 ratio in the diamond structure. This study has provided a new way to prepare diamond containing only NV − optical color centers.

The quantum anomalous Hall effect is an intriguing quantum state that exhibits chiral edge states in the absence of a magnetic field. The chiral edge states are topologically protected and robust against electron scattering, which possesses great potential applications in designing low energy consumption and dissipation less spintronic devices. The experimental conditions are required to be very high, such as extremely low temperature (< 100 mK) due to the small band gap and the greatly accurate control of the extrinsic impurities. These greatly hinder their devices from being put into applications further. Hence, it would be meaningful to search for a new Chern insulator with a large band gap and high Curie temperature. According to the first-principles calculations, we predict the room temperature quantum anomalous Hall effect in the monolayer BaPb. The nontrivial topology of this new type of ferroelectric semi-metal material derives from fully spin-polarized quadratic non-Dirac bands. The quantum anomalous Hall effect can be realized in the monolayer BaPb with fully spin-polarized quadratic px,y non-Dirac bands with the nonzero Chern number (C = 1). Because of the trigonal symmetry of monolayer BaPb material, these bands composed of px,y orbitals are at the \begin{document}$ \varGamma $\end{document} point, which is different from the Dirac state formed by the pz orbital reported previously. In addition, it can still retain its original topological properties even if strongly hybridized with the substrate. The calculated phonon spectrum shows no imaginary frequency in the entire Brillouin zone, indicating that the monolayer BaPb system is dynamically stable. By using Monte Carlo simulation, we determine the Curie temperature of BaPb monolayer toreach up to 378 K. We also calculate the magnetic anisotropy energy of the BaPb cell, defined as \begin{document}$ \Delta E={E_{100}}-{E_{001}} $\end{document}. Here, we consider two magnetization easy-axis directions, [100] and [001]. To our surprise, the MAE of monolayer BaPb is as high as 52.01 meV/cell by considering the spin-orbit coupling effect. Furthermore, the nontrivial band gap is opened with a magnitude of 177.39 meV when the spin-orbit coupling effect is included. The calculations of Berry curvature and edge states further prove that the monolayer BaPb system can realize the quantum anomalous Hall state. This discovery indicates that the monolayer BaPb materials can be used as a candidate for quantum anomalous Hall effect materials, thereby promoting the development of spintronics.

A nitrogen-doped diamond crystal with (111) orientation was synthesized with an NaN3 additive in the FeNi-C system at a pressure of 6.5 GPa and a temperature of 1,310°C, using the temperature gradient growth (TGG) method. Spectroscopic properties such as the absorption spectrum and the Raman spectrum as well as the Fourier transform infrared (FTIR) spectrum were studied. FTIR spectroscopy of the C-N vibrational modes at 1,344 and 1,130 cm−1 suggested a nitrogen content of 310 ppm. Its nonlinear optical (NLO) response was investigated using the Z-scan technique under the femtosecond regime. Due to the presence of nitrogen defects, the synthesized crystal performed large nonlinear absorption under both 800- and 532-nm wavelength excitations. However, intrinsic diamond only experiences nonlinear refraction under these two wavelength excitations. Its broadband NLO properties indicated that nitrogen-doped diamond crystals were suitable for the application of ultrafast optical devices.

考虑半导体量子点间隧穿耦合效应,研究非对称半导体三量子点分子中的弱探测光的传播特性.线性情况下,由于点间隧穿耦合和外部控制光的协同调控,探测光的吸收特性将出现共振吸收、隧穿诱导透明单窗口、隧穿诱导透明双窗口及隧穿诱导透明三窗口的转变.此外,从反常色散到正常色散的开关效应可通过改变隧穿强度及光学控制场强度来实现.对于非线性情况,发现孤子的振幅随着点间隧穿耦合系数增大呈先增大再减小随即再次增大并减小的波动变化趋势且出现最大振幅及其对应的点间隧穿耦合强度随着外部控制光场的增大而减小.此外,发现孤子的群速度随着耦合强度的增加呈逐渐减小的趋势.